Don't feel bad, this is important and you care very much about your fish.
First thing, get the GH, KH, pH and anything else you can get from the breeder. Second, if you don;t find it first I will find it as far as how much current guppies like to be in. It actually osunds like a huge stress factor and I am thinking they might not like the extra current. When I had the best luck with my guppies breeding they were crowded in a small 2.5 gallon hex with nothing more than a sponge filter.
Test the volcano with vinegar and see if reacts.
To be honest, I would set up a 10 gallon tank, cycle it with sponge filters and do everything excactly the same as you do with your fry tank. If you move the guppies in the 10 gallon and they still die I would be really suprised. Start the new tank fresh and do not use anything from the other tanks except for the fry tank. I have not tried them but THESE
filters are the best I have seen and I will never buy anything else when I set up my breeder tanks if I ever have the room. When looking for a sponge filter I would recommend the ones that require an airstone to run them for added circulation and ease of use. the ones one the site are also customizeable which is an added benefit.